1. Field of the Invention
The present invention relates to a regenerative carbon dioxide gas separator and a carbon gas separating system. More particularly, the present invention relates to a regenerative carbon dioxide gas separator and a carbon gas separating system that can separate carbon dioxide gas (CO2) contained in effluent or exhaust gases from combustion boilers and the like in an efficient and economical manner.
2. Related Background Art
Carbon dioxide gas released into the atmosphere from various industrial facilities such as thermal power plants, refuse incinerating plants, etc., are said to be responsible for the global warming caused by the xe2x80x9cgreenhouse effectxe2x80x9d. Therefore, it is necessary to reduce the volume of carbon dioxide gas released into the atmosphere. For example, in a thermal power plant, a fuel such as a petroleum fuel, a coal fuel, LNG (liquid natural gas), etc. is burned in a boiler to generate a considerable volume of carbon dioxide gas.
Conventionally, as a method for separating carbon dioxide gas from an effluent or exhaust gas, a method using an xe2x80x9cabsorption liquidxe2x80x9d containing an amine, and a xe2x80x9cmembrane separation methodxe2x80x9d using a cellulose acetate membrane or the like are proposed.
For example, Japanese Patent No. 2809368 discloses a method for recovering carbon dioxide gas by the use of an aqueous alkanolamine solution that in nonflammable. Further, Japanese Patent No. 2809381 discloses a separation system using a monoethanol amine absorption liquid, in which a heating source of a reboiler of an absorption liquid regeneration tower is optimized.
However, in such methods using xe2x80x9cabsorption liquidxe2x80x9d, absorption efficiency is not so high. For example, the volume of carbon dioxide collected by an absorption liquid containing an amine is at most about 20 to 30 times the volume of the absorption liquid. Therefore, in a large-scale combustion plant, an extremely large amount of absorption liquid should always be circulated.
Moreover, such methods using xe2x80x9cabsorption liquidxe2x80x9d require an absorption tower for absorbing carbon dioxide gas, a regeneration tower for regenerating the absorption liquid, a reboiler, and a circulation system to connect these. Therefore, the system becomes very complicated.
Similarly, in a xe2x80x9cmembrane separation methodxe2x80x9d, a pressure control mechanism is required so that only carbon dioxide gas is permeated from the positive pressure side to the negative pressure side of a separation membrane and absorbed. Therefore, the system becomes very complicated.
In addition, the allowable temperature that can be tolerated by the absorption liquids and separation membranes used in the above-described methods is about 200xc2x0 C. Thus, heat resistance of such absorption liquids and separation membranes is low. Since the temperature of most effluent gases discharged from various combustion sources, such as a boiler of a thermal plant, is 600xc2x0 C. or more, it is necessary to provide an effluent gas cooling system before introducing an effluent gas into a carbon dioxide gas separator. Therefore, the system becomes complicated, and the cost for separating carbon dioxide gas becomes high.
Given the above-described problems, the present invention is proposed. An object of the present invention is to provide a regenerative carbon dioxide gas separator and a carbon dioxide gas separating system that can separate carbon dioxide gas with great efficiency although they have far simpler configuration than conventional apparatuses or systems.
In order to achieve the above objective, a regenerative carbon dioxide gas separator according to the present invention includes: a rotatable rotor; an absorbing/separating agent housed in the rotor, for absorbing carbon dioxide gas at a temperature lower than a predetermined temperature, and for releasing the absorbed carbon dioxide gas at a temperature higher than the predetermined temperature; a first gas flow passage for passing a first gas through the rotor in a direction substantially parallel to a central axis of rotations of the rotor; a second gas flow passage for passing a second gas through the rotor in a direction substantially parallel to the central axis of rotations of the rotor; and a sealing mechanism for preventing the mixing of the first gas and the second gas, wherein carbon dioxide gas contained in the first gas is absorbed by the absorbing/separating agent and the carbon dioxide gas absorbed by the absorbing/separating agent is released into the second gas by rotating the rotor while the temperature of the first gas flow passage is set to be lower than the predetermined temperature and the temperature of the second gas flow passage is set to be higher than the predetermined temperature.
With the above-described structure, it is possible to obtain a carbon dioxide gas separator, which is more efficient, more cost-saving and more reliable than conventional devices.
The carbon dioxide gas separator may include a plurality of baskets attachable to the rotor, each having an opening in a direction of the gas flows. The absorbing/separating agent may be housed in the baskets.
Further, a regenerative carbon dioxide gas separator according to the present invention includes: a plurality of reaction chambers; an absorbing/separating agent housed in the plurality of reaction chambers, which absorbs carbon dioxide gas at a temperature lower than a predetermined temperature and releases the absorbed carbon dioxide gas at a temperature higher than the predetermined temperature; and switching means for selectively supplying one of first gas and second gas to the plurality of reaction chambers; wherein the regenerative carbon dioxide gas separator sequentially performs in the reaction chambers: absorption cycles in which the first gas is supplied to a reaction chamber to form a first gas flow passage while the temperature of the reaction chamber is maintained to be lower than the predetermined temperature, and the absorbing/separating agent absorbs carbon dioxide gas contained in the first gas; and regeneration cycles in which the second gas is supplied to the reaction chamber to form a second gas flow passage while the temperature of the reaction chamber is maintained to be higher than the predetermined temperature, and the absorbing/separating agent releases the absorbed carbon dioxide gas into the second gas.
With the above-described structure, a fixed-type regenerative carbon dioxide gas separator which is highly efficient and cost-saving can be obtained.
If the reaction chambers include heating means for heating the absorbing/separating agent to a temperature higher than the predetermined temperature, it is possible to heat the absorbing/separating agent to a temperature higher than the inflection point surely and easily.
If the absorbing/separating agent includes at least one of lithium zirconate, an alkali metal oxide, and an alkali earth metal, it is possible to realize highly efficient absorption/separation.
If the absorbing/separating agent is shaped into any of granular, porous, aggregated, tubular, deformed-plane, and linear shapes, or shaped into an aggregated or plane-structured article having through holes in a direction of the gas flows, it is possible to absorb/separate carbon dioxide gas in an efficient manner.
Moreover, if the absorbing/separating agent is supported on at least one of granular, porous, aggregated, tubular, deformed-plane, and linear molded article, or an aggregated or place-structured molded article having through holes in a direction of the gas flows, such an article is highly efficient and reliable.
If a plurality of absorbing/separating agents are provided, for each of which the determined temperature differs, it is possible to further improve absorbing/separating efficiency.
A carbon dioxide gas separating system according to the present invention includes: any of the above-described regenerative carbon dioxide gas separators; heating means for heating the second gas flow passage of the regenerative carbon dioxide gas separator to a temperature higher than the predetermined temperature; heat recovering means for cooling a gas flowing out of the first gas flow passage; and heat exchanging means for transferring heat energy from a gas containing carbon dioxide gas flowing out of the second gas flow passage to the first gas supplied to the first gas flow passage.
The carbon dioxide gas separating system may further include circulating means for supplying at least part of the gas containing carbon dioxide gas discharged from the second gas flow passage to the second gas flow passage again, and the heating means may be a regenerative burner or an indirect type of furnace for burning a fuel to heat the gas containing carbon dioxide gas circulated by the circulating means.
The heat recovering means may include a boiler for generating steam by the use of the gas discharged from the first gas flow passage, or may include the boiler, a steam turbine driven by the steam generated by the boiler, and a generator driven by the steam turbine.
The heat exchanging means may be a plate-type, tubular-type, or rotary-type of regenerative heat exchanger.